Power conversion devices using switching of power semiconductor elements have high conversion efficiency, and thus, have been widely used for consumer use, automotive use, railway use, substation equipment, and the like. The power semiconductor element generates heat by energization, and thus, requires high power dissipation and is cooled by using air or a liquid. In particular, a power semiconductor module having a large heat generation uses a cooling system using a liquid, and thus, it is important to provide a seal that secures liquid tightness of a refrigerant flow path on which the power semiconductor module is mounted. PTL 1 is disclosed as a structure in which a power semiconductor module is mounted on a refrigerant flow path and then is sealed.